It is generally known to supply commercial aircraft with conditioned air for heating and cooling when the aircraft is stationary at a gate. In this application, the term gate is meant to refer to any place that an aircraft receives or discharges passengers or cargo. This may be by way of a telescoping corridor, stairs, or any other facility. Typically, conditioned air is supplied to the aircraft from a pre-conditioned air (PCA) unit that has a ducting system associated with the gate that is a part of the airport terminal. The air is delivered from the gate to the aircraft with a flexible and usually insulated air hose. When not in use, the hose is stored under the terminal. When hooked up to an aircraft the blowers of the PCA are energized, and air flows to the aircraft. This means it is unnecessary for the airplane's fuel powered auxiliary power unit (APU) to produce conditioned air for the stationary aircraft. The pilot can turn off the APU, thus preventing the increased cost and pollution caused by burning the fuel.